using System;

using System.Text.Json;

public class Program

{

    public class Stay

    {

        public DateOnly Checkin { get; set; }

    }

    public static void Main()

    {

        var stay = new Stay { Checkin = new (2024, 10, 1) };

        var serialized = JsonSerializer.Serialize(stay);

        Console.WriteLine(serialized);

        var deserialized = JsonSerializer.Deserialize<Stay>(serialized);

        Console.WriteLine(deserialized.Checkin);

    }

}